Silane compositions and silane coupling agents are well known. The use of silane coupling agents can increase the adhesive characteristics of many bonds, particularly the bond of thermosetting resins to glass, metal and metal oxide surfaces. It is well known that the bond formed by silane coupling agents is often deleteriously affected by moisture and, occasionally, the exposure of silane-coupled bonds to humid conditions can lead to the premature failure of the bond.
To minimize the effect that moisture has on silane-coupled failures, cross-linking agents have been combined with the silane coupling agents. For example, U.S. Pat. No. 4,689,085 describes silane compositions which comprise (I) a silane coupling agent; and (II) a disilyl cross-linker compound represented by the general formula
(RO).sub.3 SiR'Si(OR).sub.3
wherein RO denotes an alkoxy group containing from 1 to 8 carbon atoms, R' is a divalent organic group, and the weight ratio of (I) to (I) is between 1:99 and 99:1 inclusive. The silane compositions are reported to be useful as primers in the production of laminates and other composite materials.
U.S. Pat. No. 5,073,456 describes multi-layer printed circuit boards and processes for preparing multi-layer printed circuit boards utilizing a silane bonding mixture consisting essentially of (I) a ureido silane, and (II) a disilyl cross-linking agent generally represented by the formula EQU (RO).sub.3 SiR'Si(OR).sub.3
wherein each R is an alkyl group containing 1 to 8 carbon atoms and R' is an alkylene group having from 1 to 8 carbon atoms.
Unfortunately, the disilyl cross-linking agents described in the '085 and '456 patents recently have been found to possess highly toxic properties as disclosed in several TSCA 8(e) submissions to the U.S. Environmental Protection Agency (for example, 8EHQ-0388-0347, 8EHQ-0392-1047, etc.). Therefore, the continued use of disilyl cross-linking agents must be closely examined and materials which can be substituted for the toxic disilyl cross-linking agents would be desirable.